Other attendees at the 900-strong event included singer Ronan Keating, actress Rosamund Pike and footballer Zinedine Zidane.
The classically understated collection takes its name from the Italian coastal resort where photographer Peter Lindburgh shot Friends of IWC, including Cate and Ewan, in May 2010. His portfolio of striking black and white photos along with an exclusive “making-of” film premiered at the gala.
Cate wore an elegant black halterneck Givenchy dress and kept her make-up minimal – all the better to accentuate her statement black and gold Schaffhausen watch – while Ewan went for a chic grey suit.
Check out the Fifties-inspired Portofino collection at iwc.com/en-us/
By Deborah Baker